1. Field of the Invention
The invention relates to seat belt restraints for securing child seats in a passenger compartment of an automotive vehicle.
2. Background Art
Occupant seat belt restraint systems comprising three-point seat belt assemblies long have been included as standard equipment by original equipment manufacturers in the automotive vehicle industry. Such restraint systems are effective for passengers of adult size and weight. In the case of child passengers, child seats are used for supporting the child within a vehicle seat assembly. Typically, the child seat is secured to the vehicle seat assembly by a seat belt specially designed to properly restrain the child seat in either the passenger-side front seat or in the vehicle rear seat. The seat belt of the restraining belt assembly for the child seat is secured to the structural floor of the vehicle passenger compartment and is routed through the child seat. The assembly has a seat belt buckle and latch plate, which can cinch the seat belt after the seat belt is secured in place.
A seat belt tension sensor is used to provide an indication of the seat belt tension as the child seat restraining belt assembly is cinched in place. It is possible, however, to xe2x80x9cover-cinchxe2x80x9d child seats, causing excess seat belt tension. Excess seat belt tension can occur, furthermore, simply by using the usual power seat motors to move the seat assembly forward in the vehicle passenger compartment. It is possible, for example, to put enough additional load on an occupant classification sensor to make an over-cinched child seat, when occupied by a child, appear to weigh as much as an adult. In these circumstances, the occupant classification sensor in the seat belt restraint system may deploy an air bag in the event of a collision, thereby presenting risk of injury to a child occupying the child seat.
The occupant classification sensor makes it possible to suppress air bag activation if the occupant of the passenger seat is a child while providing for low-risk air bag deployment if the seat is occupied by an adult. It is possible in the case of an over-cinched child seat, however, for the occupant classification sensor to make an inappropriate choice between an air bag suppression state and a low-risk deployment state, thereby causing enablement of the passenger air bag when enablement is inappropriate.
A seat belt tension sensor is used to provide an input to a restraint control module. The seat belt tension sensor output is read by the restraint control module, together with a seat weight sensor signal. That data is processed to develop appropriate occupant classification sensor response.
The seat belt tension sensor typically is located at a floor-mounted lower seat belt anchor point in the case of a front passenger seat installation. The seat belt tension sensor is sewn directly into the seat belt webbing. An additional weight signal reading caused by over-cinching a child seat belt would be sensed by the seat belt tension sensor. That reading will be subtracted by the classification sensor from the gross weight data so that the actual child seat weight data will remain in the nondeployment range for the air bag assembly.
A drawback to such conventional designs is the inability to remove and service the seat belt tension sensor without removing the entire seat belt assembly, which would include a seat belt retractor, webbing, buckle assembly, etc. The entire seat belt assembly thus must be replaced when the sensor malfunctions. This is an inefficient servicing procedure, and it can be relatively expensive for the vehicle owner.
The invention provides a solution to the problem of servicing a seat belt tension sensor in a seat belt assembly for securing a child seat on an automotive vehicle passenger seat without the requirement for removing and replacing the entire seat belt assembly. The improvement of the present invention overcomes the drawback of conventional designs by providing a so-called xe2x80x9cmini-bucklexe2x80x9d of the type presently used on seat belts for rear seat passengers in vehicles manufactured, for example, by Ford Motor Company. Such mini-buckles often are used on sport utility vehicles and minivans having removable seats.
The seat belt tension sensor and seat belt assembly of the present invention overcomes the disadvantages of prior art constructions by securing a seat belt tension sensor to an anchorage at the lower right-hand side of a front passenger seat. The end of the seat belt that is routed through the child seat is secured to the seat belt tension sensor by the so-called mini-buckle, which is formed integrally with the seat belt but which can be released in an emergency situation that would require removal and servicing of the seat belt tension sensor. This avoids removal of the entire seat belt assembly during the servicing procedure, thereby simplifying servicing operations while reducing servicing cost. The seat belt tension sensor can be replaced simply by unbuckling it from the seat belt system by using an emergency release mechanism of the mini-buckle and then removing its anchor bolt.
In practicing the invention, the seat belt of the restraint system is routed through the child seat. An anchorage for one end of the seat belt is located at the structural floor portion of the vehicle passenger compartment. The seat belt tension sensor is made a part of the anchorage of the seat belt. A latch plate extends from the tension sensor.
A mini-buckle assembly locks the latch plate to the seat belt as the latch plate is received in the mini-buckle assembly. A releasable latch in the mini-buckle assembly secures the latch plate to the seat belt.
A seat weight sensor in the vehicle passenger seat develops a passenger weight signal. An occupant classification sensor electronic control unit receives the seat belt tension output signal and the weight signal and transmits the proper occupant classification system data to a restraint control module.